Björn Roscher

Comparison of wind turbine loads inside a wake between engineering model and CFD calculation

Depending on location and inflow situations, a wind turbine experiences a variety of loads. Especially when considering that wind turbines are placed in a cluster. Inside wind farms, the wind turbines experience wake effects. This effect results in an increased turbulence intensity and therefore into higher loads onto the wind turbine components. Such increased load situation could lead to an early fatigue failure. For this reason, it is necessary to investigate the influence of wake effect on the wind turbine loading. Multiple wake models have been developed to represent and inspect the wake effects. This paper will utilize the method proposed by the IEC 61400 norm versus an inflow field generated by a Computational Fluid Model. The resulting 3D wind fields are used as an input into a multi-body simulation environment. This is done to determine the influence on the receiving wind turbine. The comparison will be inspected at the rotor hub coordinate system, as suggested by the Germanischen Lloyd, such that influencing parameter can be minimized. It was determined that in case of a partial wake inflow the results of the CFD indicate a higher load variation in bending and tilt direction.

Modelling of Wind Turbine Loads nearby a Wind Farm

Each wind turbine experiences a variety of loads during its lifetime, especially inside a wind farm due to the wake effect between the turbines. This paper describes a possibility to observe a load spectrum while considering wake effects in a wind farm by through the turbulence intensity. The turbulence intensity is distributed along the wind rose of Alpha Ventus. For each turbulence intensity, a Weibull characteristic is calculated. The resulting wind fields are used to determine the loads through a multibody simulation of an imaginary wind turbine located at FINO-1, representing a closely placed wind turbine at the outer edge of a wind farm. These loads are analyzed and summed up. As expected, the change of the turbulence intensity due to the wake effect has an impact on the internal loading of a wind turbine inside a wind farm. Based on the assumed loading conditions, the maximum loads increased by a factor of almost 2.5.